Another vote for the Bushnell TRS-25. I have one on my 22/45 and the zero never wavers and the battery seems to last forever. I put a Primary Arms Micro Dot on my new Volquartsen Scorpion, only because I wanted to try a smaller 2 MOA dot for bullseye shooting. It's very similar in appearance and function to the Bushnell. The only beef I have with the Primary Arms is that on mine, the brightness goes from a pretty good setting for an indoor range down to near invisible when I switch from #4 to #3. On my Bushnell I was using the #1 setting for slow fire and #2 for timed and rapid. Now I just use #1 all the time. If you ever read the bullseye forums, where they are known to pooh-pooh moderately priced equipment, you probably won't hear a bad word about the TRS-25.